Revert of Replace reduce-memory mode in idle notification with delayed clean-up GC.

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index ec625665968271d21922e3c299f54eb0c00b8f5d..d0e7a87ea0c04a70b64a07c798a5c7f43edf225c 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -15363,7 +15363,6 @@
 
 // Test that idle notification can be handled and eventually collects garbage.
 TEST(TestIdleNotification) {
-  if (!i::FLAG_incremental_marking) return;
   const intptr_t MB = 1024 * 1024;
   const double IdlePauseInSeconds = 1.0;
   LocalContext env;
@@ -15374,9 +15373,6 @@
   CHECK_GT(size_with_garbage, initial_size + MB);
   bool finished = false;
   for (int i = 0; i < 200 && !finished; i++) {
-    if (i < 10 && CcTest::heap()->incremental_marking()->IsStopped()) {
-      CcTest::heap()->StartIdleIncrementalMarking();
-    }
     finished = env->GetIsolate()->IdleNotificationDeadline(
         (v8::base::TimeTicks::HighResolutionNow().ToInternalValue() /
          static_cast<double>(v8::base::Time::kMicrosecondsPerSecond)) +